That type of dove tail is known in the trade as "through lump". It requires more fitting and careful attention than the standard dove tail. More addaptable to heavy wildfowling guns as it was not favoured in light game guns as it requires wider action and barrels are not as easily balanced and lightened as otherwise can be attained from typical dove tail lump and of course the chopper lump.
In heavy load wildfowling applications the through lump allows (as in your photo) the drilling of the extractor holes with little if any removal of metal on the barrels, providing much wall area to absorb chamber pressure.
Last edited by bushveld; 01/29/10 06:15 PM.
